If you're thinking of people who are unable to grow any hair on their body, that is a result of a condition called Alopecia.
what do we call the hair specialist doctor?
A lock of hair?
Pubic Hair
a lock of hair
When someone has no hair they are bald
hair follicle
The hair flip.
Theoretically, you could call that person a braider, but more likely you would call them a hair stylist.
Hair Stylist,Hair Dressers or Salonists.
Barber - Hair-Stylist - Hair-Dresser -
If his job is cutting and styling hair, then I'd call him a hairdresser.
Hairdresser, hair stylist, barber.